JPS5831695A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To improve the frequency characteristics, satisfying the properties of high specific modulus of elasticity and high internal loss at the same time, by containing an aramide fiber of flat cross section. CONSTITUTION:A nozzle having 4 in long and short axis ratio is used to spin aramide fiber, and the fiber is elongated 10 times to obtain the fiber, 30mum of long axis, 10mum of short axis and having flat cross section. The fiber is cut to 1.5mm. length to be a reinforcing member. As the base, polyethylene is used and kneaded in the ratio of 8:2 with the reinforcement member and cut into master pellets. A reinforced polyethylene sheet, 0.2mm. of thickness is obtained by extruding the pellets. This sheet is heated for ten and several seconds in far in far infrared rays, and formed by cold press after softening to obtain a diaphram.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diaphragm for a speaker, and its object is to provide a diaphragm for a speaker that has a high specific modulus of elasticity and a large internal loss.

In general, the characteristics of a speaker are largely related to the physical properties of the diaphragm used. Ru. Traditionally, paper has often been used for speaker diaphragms, but in recent years, diaphragms made of polymeric or metal materials have begun to be used. but,
No material has been found that simultaneously satisfies both the specific modulus of elasticity and internal loss required of a speaker diaphragm. Specific modulus of elasticity and internal loss have contradictory properties, and it is impossible to satisfy both simultaneously with a single material. Currently, resins mixed with flakes are considered to be effective, but in this case, a high specific modulus cannot be obtained unless the flake content is considerably increased to 5". This is due to the aspect ratio of the flakes. This is because the ratio is small and their contribution to the elastic modulus is small.In addition, materials with a high flake content tend to cause brittle fracture in speaker diaphragms, and have the disadvantage that even small impacts can cause them to break. Furthermore, in terms of weight, there is a drawback that the larger the flake content, the heavier the product becomes.The present invention solves these conventional drawbacks.

The speaker diaphragm of the present invention contains aramid fibers with a flat cross-sectional shape, and thus has the feature of simultaneously satisfying physical properties of high specific modulus and high internal loss. Here, the aramid fiber is, for example, Kev
It is made of aromatic polyamide represented by TAR-49 (trade name), and after liquid crystal spinning, the fibers are heat-treated under tension to promote crystallization.

Table 1 shows the physical properties of various fibers.

As is clear from Table 1, aramid fibers have a low specific gravity and a higher modulus of elasticity than glass fibers. Although its elastic modulus is slightly lower than that of carbon fiber, it has superior tensile strength and is non-conductive, so it can be used in indirect lead types and has a wide range of uses. In a composite material with a resin, since the aramid fiber has a flat cross-sectional shape, there is a large amount of spacing between the fibers in the composite material. And since the flaky ones have overlapping layers,
The surface area is wide and the internal loss becomes large. Therefore, by using aramid fiber with a flat cross-sectional shape as a reinforcing material, it is possible to create a speaker diaphragm material that is lightweight, has a high specific modulus, and has a high internal loss.In this case, a high internal loss can be obtained. It is desirable to use aramid fibers with a long axis/short axis ratio of at least 3 or more. Figure 1 shows the relationship between the long axis/short axis ratio of aramid fibers and internal loss. A method for producing aramid fibers with a flat cross-sectional shape is a spinning method using a flat nozzle.

There are two ways to cut the film.

□Hereinafter, one embodiment of the speaker diaphragm of the present invention will be described.

Example 1 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to give a long axis diameter of μm and a short axis of 10 μm.
An aramid fiber having a flat cross-sectional shape with a long axis/short axis ratio of 3 μm was obtained. This flat aramid fiber was cut into pieces with a fiber length of 1.6 and used as a reinforcing material. Using polyethylene as a base material, it was thoroughly kneaded with flat aramid fibers at a ratio of 8:2 and cut to produce master pellets. Using this master pellet, a reinforced polyethylene sheet with a thickness of 0.2 m was obtained using an extruder again equipped with a T-die. Next, this sheet was heated with far infrared rays for a few seconds, and when it softened, it was cold pressed to form a diaphragm.

The physical properties of this diaphragm are shown in Table 2. In addition, the base material is polypropylene instead of polyethylene.

Similar results were obtained using thermoplastic resins such as TPX, polycarbonate, and polyethylene terephthalate.

Example 2 Aramid fibers were spun using a nozzle with a major axis/minor axis ratio of 4, and then stretched 10 times to obtain a cross-sectional shape with a major axis of 3 μm, a short axis of 10 μm, and a major axis/short axis ratio of 3. Obtained flat aramid fibers. A woven fabric is made from this flat aramid fiber, then this woven fabric is impregnated with phenolic resin, the solvent is removed, and hot press molding is performed at a mold temperature of 200°C, followed by after-kissing at 160°C for 2 hours. A diaphragm was obtained in the following manner.The physical properties of this diaphragm are shown in Table 2. Similar results were obtained not only with phenolic resin but also with thermosetting resins such as epoxy.

Example 3 Aramid fibers were spun using a nozzle with a major axis/minor axis ratio of 4, and then stretched 10 times to obtain a cross-sectional shape with a major axis of 3 μm, a short axis of 10 μm, and a major axis/short axis ratio of 3. Flat aramid fibers were obtained. Then, this flat aramid fiber was
It was cut into m. Next, 20 wt% of this flat aramid fiber with a fiber length of 1.51111+ and wood pulp (NUKP
) and 80 wt % in a total aqueous solution, this was formed into a cone shape, water was absorbed, and then hot press was performed to obtain a diaphragm. Table 2 shows the physical properties of this diaphragm.

Example 4 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to obtain a cross-sectional shape with a long axis of 3011 m, a short axis of 10/jms, and a long axis/short axis ratio of 3. A flat aramid fiber was obtained, which was cut into a length of L5m. Then, 20wt% of this flat aramid fiber with a fiber length of L5m and 80wt% of high-density polyethylene synthetic pulp were mixed in an aqueous solution.

At this time, the high density polyethylene synthetic pulp has a beatingness of 21
0 mt was used, and it was thoroughly stirred and dispersed with flat aramid fibers. Thereafter, papermaking was carried out in a round mesh cylinder, and then this papersheet was heated with far infrared rays and molded with a cold press at the plating point where the sheet softened to obtain a diaphragm. Table 2 shows the physical properties of this diaphragm. Further, the frequency characteristic of a 10W speaker using this diaphragm is shown by curve A in FIG.

Similar results were obtained using thermoplastic synthetic pulp such as polypropylene or TPX instead of high-density polyethylene synthetic pulp.

In addition, curve B in Fig. 2 shows the 1st waveform using the conventional paper cone diaphragm.
It shows the frequency characteristics of the 03 speaker.

As is clear from the physical property values in Table 2 below, it can be seen that the diaphragms of Examples 1 to 4 simultaneously satisfy the physical properties of high specific modulus and high internal loss in all cases.

Moreover, as is clear from FIG. 2, the frequency characteristics are flat with few flaws and the high range is extended, which shows that flat aramid fibers are very excellent as a material for speaker diaphragms.

As described above, according to the present invention, since it contains aramid fibers with a flat cross-sectional shape, it is possible to obtain a speaker diaphragm that simultaneously satisfies the physical properties of high specific modulus and high internal loss and has excellent frequency characteristics. It is something that can be done.

[Brief explanation of the drawing]

Fig. 1 is a curve diagram of the relationship between the long axis/minor axis ratio of aramid fibers and internal loss, and Fig. 2 is a comparative curve diagram of the frequency characteristics of speaker diaphragms of two embodiments of the present invention and a conventional paper cone diaphragm. It is.゛

Claims (1)

[Claims] (1) A diaphragm for a speaker characterized by containing aramid fibers with a flat cross-sectional shape @) Aramid fibers with an elliptical cross-sectional shape with a major axis/minor axis ratio of 3 or more A diaphragm for a speaker according to claim 1, characterized in that a diaphragm for a speaker is used. (3) A patent claim characterized in that aramid fibers are used as a reinforcing material, and any one of thermoplastic resin, thermosetting resin, wood pulp, and thermoplastic synthetic pulp is mixed therein.
Speaker diaphragm 0 according to range 1 or 2